1. Field of the Invention
The present invention relates to a disc drive apparatus that records data signals in, and/or reproduces data signals from, an optical disc or a magneto-optical disc.
This application claims priority of Japanese Patent Application No. 2004-050359, filed on Feb. 25, 2004, the entirety of which is incorporated by reference herein.
2. Description of the Related Art
Optical discs, such as CDs (Compact Discs), DVDs (Digital Versatile Discs) and magneto-optical discs, are widely known. Various types of disc drive apparatuses have been developed, which are designed to drive these optical discs.
FIG. 1 shows a disc drive apparatus 201 that records data signals in, and reproduces data signals from, an optical disc 200. The apparatus 201 comprises a housing 202, a disc tray 203, and a base unit 204. The housing 202 has a tray port 202a made in the front. Through the tray port 202, the disc tray 203 can be inserted into and pulled from the housing 202 in the horizontal direction. The base unit 204 is secured to the disc tray 203.
The housing 202 comprises a lower case 205 and a top plate 206. The lower case 205 is shaped like a flat box and opens at the top. The top plate 206 closes the opening of the lower case 205. The front wall of the housing 202 has an opening, i.e., tray port 202a. 
The disc tray 203 can slide between a pulled-in position and a pulled-out position. At the pulled-in position, the disc tray 203 lies in the housing 202 after it is pulled in through the tray port 202a. At the pulled-out position, the disc tray 203 protrudes from the housing 202 after it is pulled out through the tray port 202a. The disc tray 203 has a recess 207 made in the upper surface. An opening 208 is cut in the bottom of the recess 207. Through this opening 208, the upper surface of the base unit 204, which is secured to the lower surface of the disc tray 203, is exposed upwards. A front panel 209 is secured to the front edge of the disc tray 203. The front panel 209 can open and close the tray port 202a of the housing 202.
As FIG. 2 shows, the base unit 204 comprises a disc-driving mechanism 210, an optical pickup 211, a pickup-moving mechanism 212, and a base 213. The disc-driving mechanism 210 rotates the optical disc 200. The optical pickup 211 writes signals in, and reads signals from, the optical disc 200. The pickup-moving mechanism 212 moves the optical pickup 211 in the radial direction of the optical disc 200. The mechanism 210, optical pickup 211 and mechanism 212 are attached to the base 213.
The disc-driving mechanism 210 has a turntable 214 and a spindle motor 215. The turntable 214 holds the optical disc 200. The spindle motor 215 is shaped like a flat disc and rotates the turntable 214. When the turntable 214 is rotated, the optical disc 200 is rotated, too.
The optical pickup 211 has a semiconductor laser, an objective lens 211a, and a photodetector. The laser emits a light beam. The lens 211a focuses the light beam, applying the beam to the signal-recorded surface of the optical disc 200, thus writing signals in the optical disc 200. The photodetector detects the light beam reflected from the signal-recorded surface of the optical disc 200, thus reading signals from the optical disc 200.
The pickup-moving mechanism 212 has two guide rods 215a and 215b, a lack member 216, a lead screw 217, and a stepping motor 218. The guide rods 215a and 215b support the optical pickup 211, enabling the pickup 211 to move in the radial direction of the optical disc 200. The lack member 216 is secured to the optical pickup 211. The lead screw 217 is in mesh with the lack member 216. The stepping motor 218 rotates the lead screw 217. When the stepping motor 218 rotates the lead screw 217, the lack member 216 is moved in the radial direction of the optical disc 200 because it remains in mesh with the lead screw 217. As a result, the optical pickup 211 moves in the radial direction of the optical disc 200.
The base 213 has openings 219a and 219b that are continuous to each other. The opening 219a exposes the turntable 214. The opening 219b exposes the optical pickup 211. To the surface of the base 213, which is opposite to the surface at which the turntable 214 and optical pickup 211 are exposed, there are secured the spindle motor 215, the ends of guide rods 215a and 215b, the lead screw 217, the stepping motor 218, and the like.
In the disc drive apparatus 201 described above, the spindle motor 215 rotates the optical disc 200 held on the turntable 214, while the disc tray 203 remains in the housing 202. The pickup-moving mechanism 212 moves the optical pickup 211 in the radial direction of the optical disc 200. As the optical pickup 211 is so moved, it writes signals in, or reads signals from, the optical disc 200.
In the disc drive apparatus 201 described above, an airflow develops when the optical disc 200 rotates in the housing 202. The airflow that develops as the optical disc 200 rotates performs a pumping action, drawing air from outside into the housing 202. Thus, air flows from outside into the housing 202 of the disc drive apparatus 201. Here arises a problem. The dust or the like, contained in the air coming from outside, fouls the optical pickup 211 and the like.
More specifically, dust or the like may stick to the objective lens 211a of the optical pickup 211 in the disc drive apparatus 201. In this case, the apparatus 201 can no longer reliably record signals in, or reproduce signals form the optical disc 200.
To prevent air containing dust or the like from entering the housing 202 from outside, the housing 202 may be sealed airtight. If the housing 202 is so sealed, however, the negative pressure rises in the housing 202. This may cause the top plate to sag. If the top plate sags, it may abut on the optical disc 200.
In the disc drive apparatus 201, the rotational speed of the optical disc 200 is increased to write signals faster in the optical disc 200. In the apparatus 201, however, the higher the rotational speed of the disc 200, the stronger the airflow that develops as the optical disc 200 rotates. Hence, the force that draws air from outside into the housing 202 inevitably increases.
In this case, air enters the housing 202 from outside through narrow gaps in the housing walls, due to diffusion and local pressure drop. Consequently, the dust or the like, which is contained in the air, accumulate in the housing 202. This presents the problem that the cleanliness level in the housing 202 falls within a short time.
Jpn. Pat. Appln. Laid-Open Publication No. 11-296866, for example, is a prior-art reference that is relevant to the present invention.
Jpn. Pat. Appln. Laid-Open Publication No. 11-296866 discloses a disc drive apparatus. In this apparatus, a cover covers both surfaces of the base that holds the optical pickup. However, it is difficult for the cover to prevent the optical pickup from being fouled with the dust or the like that is contained in the air flowing from outside.